Researchers want wasps that prey on pests to reproduce

BERKELEY (AP) -- Thousands of eucalyptus trees, which are being
killed by insects that are literally sucking the life out of them,
could be saved if scientists find a way to get Australian wasps to
reproduce.

In an ambitious plan, scientists hoped to use the parasitic
wasps to kill off the red gum lerp psyllids, which infest nearly
every eucalyptus tree in California. But for more than a year,
researchers at two state-run labs have failed to get the wasps to
mate fast enough to solve the infestation problem.

Although scientists have managed to get a small fraction of the
tens of thousand they need, they are still woefully short of female
wasps, the ones that attack the psyllid.

"The males of the species are kind of loose cannons," said Pat
Madsen, an arborist for the city of Tustin, where more than 1,500
trees have been infested by the red gum lerp psyllid.

"They're not taking care of the needs of the females. That's the
best way I can put it."

Donald Dahlsten, who is in charge of the project at the Center
for Biological Control at UC Berkeley, went to Australia to collect
the wasps after the psyllid somehow made its way to California in
1998. The insects tap into the veins of the tree's long, slender
leaves to feed on the sap. They then lay their eggs and cover the
leaves with a sticky wax tent.

The Australian wasps are one of the psyllid's natural
predators.

Dahlsten has been raising a few hundred wasps a time and trying
everything to get them to reproduce. He has experimented with the
lighting in the laboratory ecosystems built for them. He has
fiddled with the temperature and humidity. He has enticed them with
tiny forests built in cages, and isolated them in individual
vials.

Nothing has worked.

"A lot of times, programs like this can take two or three years"
to succeed, Dahlsten said. "But there's a lot of anxiety out there
because the trees are looking so bad."

At stake are hundreds of thousands of red gum eucalyptus, a
native of Australia that was introduced to California in the 1850s.
About 33,000 of them are in the south Orange County city of Lake
Forest, which has been particularly hard hit by the psyllid.

Because of the breeding problem, scientists have been able to
release the wasps, which are about the size of a rice grain and
harmless to humans, at only 21 sites statewide.

Although the releases have been limited, the results are
promising, Dahlsten said.

At two areas -- North Hollywood and Redwood City -- there is
evidence that the wasps are generating offspring. The hope is that
those wild wasps will begin reproducing more, making up for what's
not happening in the lab.

If that doesn't work, Dahlsten will probably return to Australia
to look for other natural enemies of the psyllid.